Reviewing for exam.. Probability question

Males and females are observed to react differently to a given set of circumstances. Ithas been observed that 70% of the females react positively to these circumstances,whereas only 40% of males react positively. A group of 20 people, 15 female and 5 male, was subjected to these circumstances.

Pick a random response
1) Find the probability that the response was negative
2) Given that the response was negative, what is the probability that it was a male?